Identification Of ALK Fusion Genes In Clear Cell Renal Cell Carcinomas And Function Research

As the most common type of renal cancer, clear cell renal cell carcinoma(ccRCC) accounts for about80%～85%. For advanced renal cancer, severalmolecularly targeted drugs have been recently developed to treat them, includingbevacizumab, sunitinib and sorafenib. Despite this remarkable growth in thetherapeutic options for advanced RCC, durable complete responses remain rare.Rearrangement and mutations of the anaplastic lymphoma kinase (ALK) genehave been implicated in the pathogenesis of multiple human cancers, where ALKrepresents a rational therapeutic target. A marked clinical efficacy has beendemonstrated for ALK inhibitor in non-small cell lung cancer, inflammatorymyofibroblastic tumor, and anaplastic large cell lymphoma with ALKrearrangements. Regarding renal cancer, ALK fusion gene was also found in renalmedullary carcinoma, RCC of unclassified and papillary subtype. Hence, it couldbe also of great interest to identify ALK aberrations in ccRCC. We screened tumorsamples of87pathologically defined ccRCC by IHC using a newly developedrabbit anti-human ALK monoclonal antibody. Four patients were positive for ALKas determined by IHC, which comprised4.59%of ccRCC. Using RACE-coupledPCR, we detected EML4-ALK fusion gene in tumors from2patients. The resultsof this study were confirmed by fluorescence in situ hybridization (FISH). Thenext step, the oncogenic activity of EML4-ALK variant1was analyzed in theimmortalized normal kidney epithelial cells HK-2by lentiviral expression vector.The colony-formation ability and proliferation ability of HK-2by lentiviralexpression vector of EML4-ALK variant1fusion genes became enhanced. Andthe ALK inhibitors TAE684decreased the proliferation of HK-2. Also HK-2bylentiviral expression vector of EML4-ALK variant1fusion genes generated subcutaneous tumours in nude mice. Moreover, Crizotinib reduced the growth oftumors. The results of this study indicated that ALK fusions exist in adult ccRCC,which provides the rationale for ALK inhibitor therapy in selected patients ofccRCC.